The present invention relates generally to eddy current inspection probes for inspecting a surface of a manufactured component, and more particularly to a probe having an improved fit with the surface of the component.
Eddy current inspection is commonly used to detect flaws in surfaces of manufactured components such as gas turbine engine components. During this type of inspection, electromagnetic induction is used to induce eddy currents in the component being inspected. An array of coils inside an eddy current probe generates alternating magnetic fields which induce the eddy currents in the component when the probe is moved near the component. When flaws are present in the component, the flow of eddy currents is altered. The altered eddy currents produce changes in a secondary magnetic field which are detected by the array of coils inside the eddy current probe. The array generates an electrical signal in response to the altered secondary magnetic field. The amplitude of the electrical signal is generally proportionate to the size of the flaw. Thus, approximate sizes and general locations of flaws may be determined using eddy current probes.
The array must be kept at a constant distance from the surface of the component being inspected to ensure the amplitude of the electrical signal is proportionate to flaw size. One way of ensuring a constant distance is by sizing and shaping the probe substantially identically to the feature being inspected. For instance, if the surface of an opening in a gas turbine engine disk such as a dovetail slot bottom is being inspected, a probe sized and shaped substantially identically to the opening is used.
Frequently, the probe is made to compress or collapse so it can fit into the opening. These collapsible probes generally have a compressible or collapsible core inside a flexible covering which holds the array. In the past, gaps sometimes occurred between the probe and the surface which also prevented the array from being positioned at a uniform distance from the surface being inspected due to variations in size and shape of the actual features being inspected.
Among the several features of the present invention may be noted the provision of an eddy current inspection probe for inspecting a preselected surface at least partially defining an opening in a component. The eddy current inspection probe comprises an expandable element at least partially defining an interior space which is expandable by introducing a pressurized fluid into the interior space from a collapsed position for inserting the probe into and removing the probe from the opening in the component to an expanded position in which the probe is sized and shaped for at least partially filling the opening and for contacting the preselected surface of the component for inspecting the surface. Further, the probe includes an eddy current array positioned over the expandable element for generating and detecting magnetic fields in the component to inspect the preselected surface of the component. The eddy current array has an outer surface shaped substantially identically to the preselected surface of the component when the expandable element is in the expanded position for maintaining the outer surface of the array at a preselected distance from the surface of the component.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.